61 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
This boiler uses indicator light combinations
Note which lights are on, off, or flashing and at what speed. Match the combination to the cards below. Do not reset until you have noted the pattern. How to read fault codes →
Tap any card for details
The boiler's internal diagnostic system has detected a fault, and you should check the specific pattern of the coloured LED lights to identify the issue.
Your boiler has stopped working because it failed to light the flame, and it needs a manual reset to try starting again.
Your boiler has automatically turned itself off because it reached a dangerously high temperature to prevent damage.
Your boiler has completely lost power and is unable to turn on, meaning you currently have no heating or hot water.
Your boiler is failing to detect that you have turned on the hot tap, meaning it cannot provide hot water to your home.
Your boiler has stopped working because it cannot detect that a flame has been successfully lit, likely due to a loose or disconnected internal wire.
Your boiler has lost all electrical power and cannot operate at all.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent any damage to the internal components.
Your boiler has identified an internal error that requires a professional manual to diagnose the exact issue.
Your boiler is trying to start up but cannot successfully light the flame after five attempts, so it has locked itself out for safety.
Your boiler has stopped working because it cannot properly detect the temperature of the water flowing through your heating system, so it is choosing not to light for safety reasons.
Your boiler has stopped working because it cannot detect a flame, most likely due to a faulty sensor that monitors the safety of the exhaust gases.
Your boiler is failing to start because it cannot accurately read the temperature of the water circulating back into it.
Your boiler has stopped working because it cannot detect a flame, meaning it is currently unable to produce heat or hot water.
Your boiler has detected that the internal air extraction system isn't reporting back correctly, so it has safely shut itself down to prevent operation without proper ventilation.
Your boiler has stopped working because it cannot detect a flame and is suffering from an electrical power interruption.
Your boiler's computer is struggling to communicate with its internal settings, which is preventing it from safely starting the flame to heat your water or home.
Your boiler has lost its brain, as the control system is failing to communicate correctly with the main circuit board.
Your boiler has lost the ability to control its internal settings, likely because of a communication error between its main computer chip and the heating system.
Your boiler has stopped working because its internal computer chip and the control board are not communicating correctly.
Your boiler has detected a communication problem between its internal computer brain and the control system, preventing it from safely starting the flame.
Your boiler's computer memory chip is not communicating correctly with the main controls, meaning the unit cannot safely start the burner.
Your boiler is struggling to detect water moving through it, likely because the internal water pressure has dropped too low or a sensor is misreading the situation.
Your boiler has stopped heating because it cannot detect enough water moving through the system to operate safely.
Your boiler has failed to light the flame properly or is struggling to maintain it, causing the safety system to shut down.
Your boiler has failed to light the flame needed to heat your home's water.
Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent damage.
Your boiler has detected an issue with the ventilation system or internal fan, which prevents it from safely getting rid of waste gases.
Your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.
Your boiler's temperature sensor is providing incorrect readings, so it has purposefully shut down to prevent overheating.
Your boiler has lost the ability to measure the temperature of your hot water, so it has safely shut down to prevent overheating.
Your boiler has detected heat or a flame inside when it should be turned off, so it has purposefully locked itself out to keep you safe.
Your boiler has lost the ability to accurately measure the temperature of the water circulating back from your radiators, so it has safely shut down to prevent overheating.
Your boiler has detected an issue with the sensor that monitors the temperature of the exhaust fumes, causing it to shut down for safety reasons.
Your boiler is struggling because it cannot balance the temperature between the water leaving and returning to the unit, suggesting a potential flow restriction or sensor disagreement.
Your boiler has detected that the air circulation system is not running at the correct speed, which prevents it from firing up safely.
Your boiler has detected that hot water is not flowing through your heating system properly, so it has shut down to prevent overheating.
Your boiler has detected an internal software or electronic problem that prevents it from running, and it requires a qualified engineer to investigate.
Your boiler has locked itself out because the reset button has been pressed too many times in a short window, often because an underlying problem hasn't been fixed.
Your boiler is struggling to read the outside temperature because the external weather sensor is disconnected or broken.
Your boiler is having trouble 'talking' to its external wall-mounted controller, meaning it has stopped responding to your temperature settings.
Your boiler has accidentally entered a testing mode used by engineers, which means it is currently operating at a very low power setting and may not provide enough heat or hot water.
Your boiler has detected a critical internal error in its safety monitoring system and has automatically shut down to prevent unsafe operation.
Your boiler has failed to light the burner after trying to start and requires a professional inspection of the ignition system.
Your boiler has detected an internal safety error where it thinks a flame is present when it should be switched off, causing it to lock itself out to prevent a hazard.
Your boiler's internal computer is failing to communicate with a key electronic key, meaning the system cannot reliably start or maintain a flame.
Your boiler has detected an internal computer error and is unable to start or maintain its flame, so it has shut down for safety.
Your boiler is struggling to circulate water properly or is sensing that it is overheating instantly, causing it to shut down for safety.
Your boiler has stopped working because it is not receiving a stable power supply or is failing to light the burner safely.
Your boiler's computer is experiencing a memory error and cannot detect the burner flame, meaning it has shut down for safety.
Your boiler is failing to start because it cannot detect that the internal fan is spinning correctly to vent exhaust gases safely.
Your boiler is failing to shut off the gas supply properly after it has finished heating, which poses a significant safety risk.
Your boiler has stopped working because it is struggling to detect heat or confirm a flame is burning safely, so it has shut down to protect itself.
Your boiler has detected that the exhaust gases are becoming dangerously hot and has shut down to prevent damage or safety issues.
Your boiler has failed to light because it cannot detect a flame, meaning you currently have no heating or hot water.
Your boiler is failing to ignite because it is not receiving enough gas to produce a flame.
Your boiler has detected that the water inside it has become dangerously hot and has shut itself down to prevent damage or safety issues.
Your boiler is failing to detect when you turn on the hot tap, so it isn't heating the water for your shower or kitchen faucet.
Your boiler has lost all power to its display panel, meaning it cannot detect when you turn on the hot tap or start your heating.
Your boiler has completely lost power and is unable to turn on, meaning you currently have no heating or hot water.
Your boiler has detected that it is running much hotter than it should be and has shut itself down as a safety precaution to prevent damage.
BoilerFaultCodes